Berlin (dpa) — Whether you’re writing text messages, emails or notes on your smartphone, your thumbs are always busy. But spend too much time typing on a touchscreen and eventually you’ll start to notice a pain in your hand. After all, our thumbs are not really made for hours of tapping and swiping on a smartphone display. To make matters worse, smartphones have grown increasingly large and heavy in recent years, and many high-end models now weigh more than 200 grams and require serious hand acrobatics to stretch across screen diagonals of more than 6 inches. Experts are warning that the requi…